When this
document was originally written all the links to websites were
active. Over time some of these web pages have been removed
by their owners and the data can no longer be seen. For such
sites we have removed the now non-functional hotlink but left
the reference in place with a note that it is now a DEAD LINK.
This allows us to give credit to the original source of the
data even though we can no longer direct you to it.

The
application of a chemical freezing point depressant to a roadway
prior to precipitation events so as to prevent the bonding
of snow and ice to the road surface. Mechanical snow and
ice removal usually follows the precipitation event.

This document
is one of a series that deals with non-point source (NPS) pollution
problems in British Columbia by proposing BMPs to eliminate
or reduce such pollution. It provides guidance and information
to local governments and road maintenance contractors concerning
BMPs that minimize the impact of roadsalt on roadside vegetation,
transportation corridor infrastructure, surface water and ground
water.

this
document contains Best Management Practices to help
mitigate Non-Point Source Pollution problems in British
Columbia

Public safety is the first priority and must not be sacrificed
for more economical winter maintenance procedures. However,
the cumulative effect on public safety over the lifetimes
of the individuals, which includes contamination of drinking
water supplies and corrosion of road infrastructure and vehicles,
must also be considered. This document recommends cost-effective
ways to reduce roadsalt and de-icer damage to infrastructure,
vegetation and water resources without compromising public
safety.

It is intended
for public works departments and local environment committees
which supervise or advise on the winter maintenance
of roads and streets within municipal jurisdiction. The intention
is to supplement, not replace, the current British Columbia
Ministry of Transportation and Highways accepted practices
which are documented in a technical maintenance manual (BC
MOTH, 1995). Refer to this manual, which may already be used
in some municipalities, for specific operational details.

This document
reviews measures that British Columbia municipalities can use
to reduce the pollution of the environment by roadsalt and
de-icers without compromising road safety. These include a
reduction in salt use by following application guidelines,
replacement of some salt with sand or ploughing. Pre-wetting
the salt or sand/salt mixture can make it more effective thus
reducing the amount that needs to be used. Advanced equipment
such as special snow ploughs, remote monitors, automated de-icer
sprays, infra-red pavement temperature monitors, spreaders
and pavement friction monitoring devices can also reduce salt
use. Anti-icing techniques and materials can also be used.

There are
alternatives to roadsalt which are more effective and less
damaging to water supplies and the environment but their
costs are significantly higher. However, the total cost to
society should be considered, not just the capital cost of
the roadsalt. One can also use alternative winter maintenance
practices. Changes in driver behaviour and expectations would
reduce the need for as much salt and maintenance if dry,
bare roads were not expected. Changing snow dumping practices
to eliminate dumping in sensitive areas would reduce the
environmental damage caused by what salt was still required.
Eliminating some contaminants in roadsalt would reduce the
harmful effects of roadsalt use.

there
are alternatives to common roadsalt which are more
effective and less damaging to water supplies—the
total cost to society should be considered, not
just the capital cost
of the roadsalt

There is a list of roadsalt and winter maintenance websites in
Section 5.1.

In British
Columbia, each municipality determines its own winter road
maintenance operations, which, for many communities, relies
heavily on the use of salt as a road and street de-icer. This
BMP document attempts to provide guidance to BC communities
so that they are better able to protect their natural resources
and quality of living without compromising the level of winter
maintenance services. Because road safety remains the top priority
when looking at measures that reduce the flow of roadsalt into
the environment, this document focuses on examples of successful,
cost-effective initiatives that do not compromise safety. This
document also provides technical information, resources and
guidance to encourage and facilitate development of effective
local plans to reduce the impact of roadsalt.

Case studies
elsewhere demonstrate that levels of service need not suffer
due to changes or reductions in application of
roadsalt. Following these selected BMP's, local governments
may notice significant savings in addition to environmental
benefits. There are already many municipalities in British
Columbia that have advanced winter maintenance programs and
employ many of the measures outlined in this document. They
are an excellent resource for other communities that are
working to establish more conscientious winter maintenance
practices.

this
document focuses on examples of successful, cost-effective
initiatives
that do not compromise safety—communities
in BC are susceptible
to water quality degradation
as a result of roadsalt

Winter maintenance
is an indispensable operation that provides safe winter driving
conditions for BC residents. The goal is fewer accidents and
thus lower repair costs for automobiles, and reduced medical
and job loss costs for people. There are a variety of tools
used to clear roadways of snow and ice; plowing and road salting
are only the primary ones.

Since the
early 1950s, roadsalt has been applied extensively in North
America (14 million tons
in the USA in 1996) to de-ice roads for the purpose of providing
safe and convenient driving conditions. Over time, the use
of roadsalt has become commonplace; the amount used in British
Columbia increased rapidly. There was about a 40 percent
increase through the 1980s (Bedford, 1992).

In the 1970s,
it became widely recognized that the ever-increasing use of
salt to maintain clear roadways is not without costly
consequences. Damage due to roadsalt on roadside vegetation,
wildlife, soil, road surfaces, bridges and automobiles, as
well as the contamination of surface and drinking water,
have generated concern about the use of roadsalt for de-icing.

Environment
Canada evaluated the toxicity of various sources of stormwater
and found that run-off from multi-lane divided
highways with traffic densities over 100,000 vehicles per
day had the highest frequency of severe toxicity of the sources
tested. This was due to the quick contaminant release during
snowmelt, enhanced mobility of metals in chloride-rich run-off
and high concentrations of road salt (CWWA,1999).

In parts
of Canada and the United States, ground water has been contaminated
to the degree that it is no longer potable and
some lakes have suffered environmental impacts.

The transfer
of roadsalt and other de-icers from delivery trucks to the storage
facility, and from the storage facility to the spreader trucks,
may be of more environmental concern than the actual storage of
the roadsalt. Ground water in Heffley Creek, BC (just north of
Kamloops) was contaminated in 1994 by spillage during handling
and storage at a salt storage facility. Salt and sand was stored
in front of the storage facility and not under cover on an impervious
surface. The incident demonstrated that communities in BC are
susceptible to water quality degradation as a result of roadsalt.
Generally, the spillage which may occur while transferring the
salt to and from the storage piles is of more environmental concern
than long term storage, when a proper storage facility has been
constructed. This spillage must be cleaned up immediately to prevent
chronic contamination of the local area.

it
is widely recognized that the ever-increasing
use of salt to maintain clear roadways is not without
costly consequences—the
actual annual cost of salt-related
damage approaches 15 times the
cost of purchasing and applying
the roadsalt

The initial cost of roadsalt is low compared to most alternative
treatments; however, studies indicate that the real cost of
applying roadsalt is much higher than the capital cost of the
material. The USEPA reports that the actual annual cost of
salt-related damage approaches 15 times the cost of purchasing
and applying the roadsalt. This is due to damage to roads,
vehicles, bridge decks and superstructures, water supplies
and vegetation. This cost must be weighed against the cost
of property damage and personal injuries resulting from slippery
roads which result in higher accident rates. A further cost
to consider is legal suits arising from injuries occurring
due to roads not being maintained to an acceptable standard.

Conventional
roadsalt is primarily common table salt (sodium chloride or
NaCl). Because of this, it is rarely viewed as potentially
toxic or harmful. In reality, roadsalt can be very damaging
to the environment. Roadsalt can have serious impacts on water
quality and specific BMP's have evolved to protect water resources.
In addition, a number of other chemicals are often added to
roadsalt to depress the freezing point, reduce the corrosion
of vehicles and structures and prevent the roadsalt from caking
or clumping so that it may be readily spread; roadsalt usually
contains various impurities as well. Environment Canada has
included roadsalt and other de-icers in their second Priority
Assessment List of potential toxic substances under the Canadian
Environmental Protection Act.

roadsalt
can have serious impacts
on water quality

Roadsalt is typically mined as the ore halite and transported
to various stockpiles from which it is distributed for use as
a de-icing chemical. Roadsalt acts by lowering the freezing point
of water. NaCl is effective down to about -7° Celsius and
CaCl2 will still work several degrees lower but CaCl2 costs more.
When the salt crystals are dissolved by moisture, the brine formed
is then able to melt or dissolve crystals of snow and ice, thereby
clearing the roadway for traffic. However, the effects of the
sodium chloride solution do not end there.

The sodium
chloride brine and solids enter the surrounding environment
in runoff, spray, aerosols and dust from traffic, deposition
from ploughing and snow removal. Negative impacts can include
damage to vegetation, soils and wildlife, contamination of
surface and ground water (including drinking water supplies)
and corrosion of metals, concrete and other materials. This
document is concerned principally with the impact of roadsalt
on water quality and other impacts are not discussed. However,
if less roadsalt is used the effects on soils, vegetation and
animals will also be reduced.

Recent studies
in southern Ontario showed that only about 45% of the applied
roadsalt runs off; the rest contaminates shallow
aquifers. Considering the past and present rate of roadsalt
application in Ontario, ground water will soon be contaminated
with sodium and chloride beyond safe levels. Since there
is a lag period before the salt shows up in ground water,
the problem with contaminated drinking water will continue
to get worse before it gets better, even if road salting
stops.

The accepted
chloride level in drinking water is around 250 mg/L as set
by the USEPA and the Ontario Ministry of Environment.
Pore waters from the unsaturated zone adjacent to Metropolitan
Toronto Highways had measured chloride levels of 14,000 mg/L
in 1987 (Pilon and Howard, 1987).

Mass balance
and steady state calculations, based on current application
rates in Ontario and measured loss rates, indicate
chloride will reach 400 mg/L and sodium 250 mg/L (Howard
et al, 1993). Ultimately the salt will start to show up in
the Great Lakes (Howard et al, 1993; Toronto-1995). There
are no similar studies available for British Columbia.

Sodium is highly soluble and a proportion
of it may end up in ground water or surface water.

Sodium ions
may bind to soil particles in roadside soils causing other
ions, often heavy metals, to be released into the water
in place of sodium. This exchange typically causes harmful
changes to soil structure and properties.

High concentrations
of sodium in the soil and water may be toxic to plants. High
concentrations of sodium in the human diet
may lead to many conditions such as hypertension, cardiovascular
disease, metabolic disorders, renal diseases and cirrhosis
of the liver. However, water would become unpalatable to
most people before these conditions would arise.

ground water
will soon be contaminated
with sodium and chloride
beyond safe levels
—sodium
is highly soluble and a
proportion of it may end up in
ground water or surface water
—
chloride migrates through soils and
accumulates in underground
water supplies

Sodium may also alter the pH of the surface water; Na+ ion exchange
releases H+ ions from the soil thereby making the water more
acidic. Changes in pH have been known to greatly exaggerate the
effects of certain ambient toxic substances upon aquatic life.

Chloride is prone to migrate through soils and accumulate in
underground water supplies.

Chloride
is relatively unreactive, but has been known to contribute
to density stratification, as a component of dissolved salt
in small lakes, preventing the ecologically important seasonal
lake overturn. Chloride tends to be somewhat less toxic to
animals and plants than sodium. However, too much chloride
makes water unpalatable and eventually unfit to drink.

There are
abundant examples of extensive drinking water contamination
resulting from applying sodium chloride to roads. In the United
States, Massachusetts and New Hampshire in particular, the
costly replacement and/or abandonment of wells due to chloride
contamination has occurred often enough that, in many cases,
applying salt to roads has been discontinued in problem areas
(Chollar, 1996; Minsk et al., no date).

A survey
of wells near Ottawa, Ontario in 1979 showed that levels of
chloride resulting from nearby application of salt to the roads
exceeded the Ontario Ministry of Environment public water supply
criterion (Minsk et al, no date). In British Columbia, the
community of Heffley Creek suffered severe drinking water contamination
from stored roadsalt and individual wells had the quality of
their water impaired.

Cyanide is highly soluble and will contaminate surface waters.
It is also prone to migrate through soils and accumulate
in underground water supplies.

Iron cyanide
may be added to roadsalt as an anti-caking agent at levels
reaching at least 45 mg total cyanide per 1000 kg of roadsalt.
Roadsalt containing iron cyanide (ferrocyanide or ferricyanide)
as an anti-caking agent should not be used. There are other
environmentally safe replacements for iron cyanide. This cyanide
content may not be labelled or it may be called 'yellow prussiate
of soda'. UV light breaks down the chemical bond releasing
free cyanide.

British
Columbia is a large and diverse province. There are significant
differences in regional and site-specific climate, biology,
geology and geography which are important in determining the
impact of de-icing chemicals. For example, soil composition,
drainage patterns, moisture content, timing and both total
quantity of salt applied as well as the concentration of salt
per km are a few characteristics recognized as important in
determining the sensitivity of an area to salt damage. Because
the impact of roadsalt is so site-specific, it is very difficult
to make broad recommendations for all British Columbia municipalities.

each
community should examine
its potential susceptibility to
environmental damage from de-icing chemicals and implement
winter maintenance strategies that will
protect their resources

Some characteristics that often pre-dispose an area to potential
water quality impairment from roadsalt include regularly
salted roadways in association with:

highly
permeable soils (low clay content) with low to moderate overall
precipitation that may allow salt to filter into aquifer
waters, but not enough rainfall to flush the salt through
the soil or aquifer,

shallow
or poorly designed wells, and

high
gradient slopes over impermeable soils that drain directly
into low volume, slow moving water bodies.

Often, as
was the case in Heffley Creek's 1994 water contamination, water
quality degradation due to roadsalt goes unnoticed for years
until the problem is relatively severe. Each community should
examine its potential susceptibility to environmental damage
from de-icing chemicals and implement winter maintenance strategies
that will protect their resources.

In British
Columbia, several coastal lakes are known to have had their
normal calcium and carbonate dominated chemical equilibria
altered such that sodium and chloride are now the dominant
ions (Warrington, 1998). One lake is on the highway between
Terrace and Kitimat and another between Port Alberni and Long
Beach. These are lakes adjacent to highways with snow and ice
problems which happen to have convenient scenic pullouts along
the lakeshore where snow, containing salt, was pushed over
the bank during removal operations or else roadside snow and
salt simply ran directly into the lake during the spring thaw.

The source
of the Heffley Creek ground water contamination was inadequate
salt handling and storage outside the storage facility that
had been releasing salt into the soil for years. Heffley Creek
residents were supplied with bottled drinking water, suffered
damage to gardens and other vegetation and may also have suffered
damage to water filtering systems, pipes and fixtures as a
result of this contamination. The total remediation cost of
the contamination was about $2,000,000 which included land
purchases and construction of a new salt storage facility.

communities
in British Columbia are
susceptible to water quality
degradation as a result of improper
salt storage and application

Supplying
drinking water, sealing a gravel pit, upgrading the water supply
and testing and monitoring, came to $635,000. While normal roadsalt
application operations would not be expected to cause contamination
at the levels observed in Heffley Creek, the incident demonstrates
that communities in British Columbia are susceptible to water
quality degradation as a result of improper salt storage and
application. Since salt application, roadway area, and traffic
volume all continue to increase, it is prudent to take steps
to protect water resources by preventing impacts rather than
attempting remedial measures later.

Nine strategies
to reduce or eliminate the risk to water quality caused by
roadsalt are discussed below. These are:

The state
of West Virginia uses 100,000 to 140,000 tons of roadsalt,
or more, in an average to severe winter. They may have up to
73,000 tons stockpiled at any one time. This salt costs them
an average of $35.00 ton; it is the cheapest (capital cost)
de-icing material available.

In the USA,
highway de-icing accounted for 60% (20 million tons) of the
31.5 million tons of NaCl used in 1994. No other use exceeded
10% (WVDOT, 1997). Similar data is not available for British
Columbia but these examples give an idea of the magnitude of
roadsalt use. In addition to improved salt storage and handling,
the simplest way to reduce the environmental impact of roadsalt
is to reduce the amount of salt applied.

the
simplest way to mitigate the
environmental impact of roadsalt is
to reduce the amount of salt applied

Follow application guidelines.
In many cases, applying less salt is practical without compromising
road safety. Without specific guidelines, operators desiring
to do the best possible job of clearing a roadway may err on
the side of caution and apply too much roadsalt. To prevent
over-application, established amounts of salt per unit area
for specific temperature ranges and timing, with respect to
snowfalls, should be calculated. Crews should be well trained
to adhere to the standards and ensure that application rates
are consistent. There should be regular reviews and adjustments
to the materials and amounts applied as conditions dictate.
These measures alone have been shown to reduce salting and
sanding by as much as 30 percent (Michigan, 1996). Reducing
the proportion of salt added to the sand helps too.

Consider sanding.
Another
means of reducing the amount of roadsalt is to rely more on sand
as an abrasive. Good judgement is required when using abrasives;
they may cause more environmental problems than they solve. It
depends on the abrasive used and what effect it has on infrastructure,
air quality, and watercourses.

Rely on ploughing.
Ploughing snow is more economical than melting it with chemicals
(Lawson, 1995). In general, mechanical removal should be used
in preference to salting where both methods are shown to be equally
effective, economical and practical.

Table 1 is taken from the British Columbia
Ministry of Transportation and Highways, Maintenance Services
Manual, and provides minimum roadsalt application rates to
be used by winter maintenance contractors. These rates can
be used as a basis for comparison with local salt use rates.

Table 1. Roadsalt Application Rates

Application

Description

Application
Rate

light
application

to
prevent black ice when the surface
temperature is near freezing with light snow or sleet

60
kilograms per two-lane
kilometre (about 1/20 cubic
metre)

average
application

early
in the day when the surface
temperature is -4° Celsius and rising
under snow, sleet or freezing rain
conditions

85
kilograms per two-lane
kilometre (about 1/14 cubic
metre)

heavy
application

early
in the day when the surface
temperature is -4° Celsius and stable
or when the surface temperature is
-6° Celsius and rising or late in the
day when the surface temperature
is -4° Celsius and rising, under
conditions of packed snow or ice on
the highway surfaces

130
kilograms per two-lane
kilometre (about 1/9 cubic
metre)

The services manual contains other useful information, and should
be consulted.
Details about the manual can be found in the Information
Resources section of this document

Applying
water or some de-icing solution to roadsalt and/or sand before,
or during, application is a process known as pre-wetting (Gustafson,
1992). The liquid coats the particles and, upon contact with
the roadway surface, the salt or sand embeds itself in the
ice or snow (Bodnarchuck et al, 1994).

Pre-wetting
has a capital cost which must be weighed against the environmental
costs of not using this more efficient process. Pre-wetting
decreases the amount of roadsalt or sand required without decreases
in levels of service. However, the increased costs due to pre-wetting
and the decreased cost of using less salt and sand may not
be equal.

pre-wetting
decreases the amount of
roadsalt or sand required without
decreases in levels of service—pre-wetting
does not necessarily
require large and expensive equipment
—
savings in salt, time and money can
be significant

Experiments in
1993 and 1994 by the British Columbia Ministry of Transportation
and Highways in pre-wetting salt with calcium chloride CaCl2
and magnesium chloride MgCl2 brines resulted in
large reductions (as much as 53% in one instance) in total
de-icing chemical
applications (Bodnarchuck et al, 1994). The sand is also embedded
in the snow and ice and does not get washed or blown off the
road surface. This means that less roadsalt and sand needs
to be applied to achieve the same effect, resulting in less
runoff. Smaller sand particles are used, resulting in less
vehicle paint and windshield damage. These results may justify
the extra capital cost.

A
variety of liquids may be used for pre-wetting roadsalt. These
include sodium chloride, calcium chloride, magnesium chloride,
potassium acetate, and calcium magnesium acetate in brine solutions.
Water can also be an effective pre-wetting agent provided that
the temperature is relatively high.

Each
solution has different properties and may behave differently
due to the chemical characteristics and the method of pre-wetting
employed (for more detailed information, see the document FHWA-Effective
Anti-icing Program under the heading On-line References in
the Information
Resources section of this document).

Pre-wetting
does not necessarily require large and expensive equipment
purchases. There are three basic techniques of pre-wetting:

injecting
a pre-wetting chemical into a material stockpile in specific
amounts,

spraying
the liquid into a full spreader or into the solid chemical
as it is being loaded, and

wetting
the material with a spray system as it is spread (Ketcham
et al, 1996).

The Information
Resources section of this document identifies documents that
provide instruction on how to modify trucks, spreaders, and
garages to facilitate pre-wetting. While there is an initial
investment in time, experimentation and training required,
the eventual savings in salt, time and money can be significant.

The following
are some of the benefits and concerns associated with pre-wetting:

The melting
action of salt is sped up by the additional moisture, especially
when the snow is cold and dry.

The wet
particles tend to adhere to the pavement surface or embed themselves
in the ice or snow.This
results in less waste due to scattering so less roadsalt can
be used and also results in improved vehicle traction.

The effective
temperature range of roadsalt can be increased by pre-wetting
with calcium chloride CaCl2 and/or magnesium chloride
MgCl2.

It is
important to note, however, that like NaCl, these other compounds
contain chloride. Therefore, the total volume of de-icers
applied should decrease to offset the additional chloride
from the pre-wetting solution.

Roadsalt
that is pre-wetted with calcium chloride CaCl2 tends
to retain moisture and remain on the roadway longer than
NaCl in its
own brine. This may result in less total roadsalt being applied
since less frequent applications are required.

The technology
and equipment used in winter maintenance operations is advancing
continually. There are an enormous variety of tools that can
be used to increase efficiency and safety and to reduce costs.
Some of these tools are discussed below:

Special
snow ploughs
Several
specialized snow ploughs are available that are effective for
removing specific types of snow and ice for operating under
different road, highway and street conditions (O'Doherty,
1992). Some examples of different ploughs are:

one-way
front ploughs,

reversible
ploughs,

four-way
articulated ploughs,

underbody
ploughs, and

side
wings (Ketcham et al, 1996; Michigan, 1996).

Materials
used for blade edges include synthetic polymers, rubber, steel
and carbide inserts. According to the Washington State Department
of Transportation, polymer edges are useful for removing slush
(Ketcham et al, 1996) from streets and highways. It is therefore
only necessary to reduce packed snow to slush, rather than
fully melt it, which requires only half as much salt (Ketcham
et al, 1996; Kuusela et al, 1992).

However,
this environmentally beneficial reduction in the amount of
roadsalt used has an economic cost since a second pass is required
to remove the slush. There are also snowplough scoops designed
to make snow plough operations more efficient. Note that ploughing
after de-icing salt has been applied to snow and ice results
in the deposition of salt off the roadway. This is both a considerable
waste of salt and a potential threat to the environment which
is not always avoidable.

Remote monitors
These transmit information about roadway conditions and thus
may facilitate timely and appropriate winter maintenance measures.
Such monitors are only a component of an integrated road (or
street) weather information system. In addition to real-time
pavement temperature, dew point, humidity, air temperature, wind
velocity and direction and the amount of de-icing chemical on
the pavement; they may have processing and display capacities
to assist maintenance managers choose the best maintenance measures
(Chollar, 1996; Ketcham et al, 1996). Such integrated systems
are used by highway and urban maintenance staff alike (Minsk
et al, no date; Nevada, 1995).

Pavement temperature monitors
These are very useful and much less expensive than fully integrated
remote monitors. Pavement temperature is the main factor in the
formation, development and breaking of a bond between fallen
or compacted precipitation and the road surface as well as the
effectiveness of chemical treatment (Ketcham et al, 1996).

Remote monitors
that lie beneath the road surface can indicate pavement temperatures,
in particular trouble spots, near or on a bridge for instance,
so that action can be taken immediately when there is the risk
of dangerous conditions. It is even feasible to have speed
limits over bridges regulated by automated road condition monitors.
Thermisters are used in several locations in British Columbia.

Automatic de-icer spray systems
These are available for trouble spots such as bridge decks; a
high pressure nozzle and sprayer are embedded in the roadway
itself and activated remotely or automatically when sensors indicate
there is a need (Minsk et al, no date).

Infrared pavement temperature monitors
These can be fitted to trucks so maintenance supervisors can
determine the most efficient rate of
de-icer or abrasive application
required (Lawson, 1995).

an
efficient and precise spreading
mechanism is one very effective
way to mitigate the impact of
roadsalt on the environment

Spreaders
These and other application mechanisms are one of the most fundamental
pieces of winter maintenance technology with regard to de-icing
chemicals. They can range from somebody in the back of a pickup
with a shovel and some salt, to a state-of-the-art spreader truck
with tanks for liquid de-icing chemicals, automatic speed regulated
application and various other technologies. The range in capital
cost is, of course, equally broad.

Having an
efficient and precise spreading mechanism is one very effective
way to mitigate the impact of roadsalt on the environment.
An even distribution of salt, applied at a consistent, pre-determined
rate, with minimal scattering of salt particles cuts down dramatically
on the amount of material applied. Special spreaders also allow
for the implementation of liquid de-icer, anti-icing and pre-wetting
applications which, themselves, can be very effective means
of reducing roadsalt application.

Highway
authorities in Finland report that a liquid roadsalt solution
allows for 50 to 75 percent reductions in roadsalt application
over granular roadsalt, because of application accuracy (Kuusela
et al, 1992). Each community should examine its own needs and
consider the most effective device for their own de-icing operations.
Future savings in materials, wages, and community-wide salt
damage should be considered when comparing the cost of various
spreaders.

Pavement friction monitoring devices
These can be used to determine precisely how slippery the roadway
is. Such a device attaches to a vehicle and measures the friction
coefficient of the road surface. The operator can then make an
informed decision as to whether application of roadsalt is needed.

The term
anti-icing is one that has emerged relatively recently to describe
a new approach to winter maintenance that differs from traditional
de-icing methods. Anti-icing is the timely application of chemical
freezing point depressants to roadways before snow and ice
accumulate. This prevents the formation of a bond between slippery
snow and ice and the roadway, thereby facilitating mechanical
removal (Ketcham et al, 1996). Anti-icing allows for a very
high level of traffic safety at low cost and significantly
reduces the amount of roadsalt used.

Salt is
no longer applied in quantities required to melt downward through
a heavy layer of snow and ice. Because the required amount
of de-icer is reduced, it then becomes feasible to use more
expensive and more specific chemical alternatives to roadsalt.

anti-icing
allows for a very high level
of traffic safety at low cost and
significantly reduces the amount
of roadsalt used—to use anti-icing techniques, a winter
maintenance operation may only
need minor adjustments
—
an essential component for a
successful anti-icing program
is operator training

Many of the winter maintenance tools described earlier,
such as special ploughs and weather information systems
are components of anti-icing programs. Anti-icing consists
of preventative winter maintenance measures that may
vary depending on climatic, roadway and traffic conditions
as well as timing. This practice requires the use of
considerable judgement and experience, the methodical
use of available information, and the ability to promptly
coordinate and mobilize operations (Ketcham et al,
1996).

To use anti-icing
techniques, a winter maintenance operation may only need minor
adjustments. Often, it is discovered that anti-icing is being
practiced without it being recognized as such. Some of the
more effective anti-icing tools include liquid anti-icing chemicals
(liquid de-icers) and accurate local weather information. In
some areas these techniques alone are sufficient to eliminate,
or greatly reduce, the use of roadsalt. Liquid spreading mechanisms
can be constructed at relatively low cost.

These tools,
along with experience of local road conditions, may be enough
to achieve goals like improved roadway conditions, fewer working
hours per week for winter maintenance operators and reduced
impact on the environment (Keep et al, 1995).

An essential
component for a successful anti-icing program is operator training.
Winter maintenance experts in North America and Europe alike
stress the importance of training for anti-icing. Operators
must have a good understanding of what the options available
to them will achieve and use a systematic approach. Standards
and calibration charts are important parts of an anti-icing
operation but are ineffective without an operator who is aware
of their function and impact. Operator training is one benefit
of inter-community exchanges of information and resources that
can be especially valuable. There are also consultants who
may be contracted to educate crews and managers about anti-icing
practices.

The above
material only summarizes some basic information on anti-icing.
Further independent research on the topic is recommended. For
references see the Information Resources section of this document.

Several
freezing point depressants are available for road de-icing
as alternatives to NaCl. Their efficiency as de-icers, and
their relative effects on the environment need to be reviewed
on an individual basis.

The initial
cost of NaCl is quite low compared to most alternatives, but
studies have indicated that the real cost of applying roadsalt
is much higher than the initial cost. The US Environmental
Protection Agency reported that the actual annual cost of salt
related damage for 1976 was 15 times the cost of purchasing
and applying the roadsalt (D'Itri et al, 1992).

Figures
for the full cost of applying roadsalt in BC are not available,
but they are likely similar and substantial. The high actual
cost of salt damage has not been enough to dissuade most agencies
in North America from using salt.

However,
the Washington State and Oregon State Departments of Transportation
have eliminated or vastly reduced sodium chloride in their
winter maintenance programs because of the high overall costs
associated with its use (Keep et al, 1995). They have used
anti-icing strategies, including the application of calcium
magnesium acetate as the principal freezing point depressant.

the
actual annual cost of salt related
damage approaches 15 times
the cost of purchasing and
applying the roadsalt
—there are alternatives to roadsalt
available that cause less
environmental damage

Calcium Chloride (Ca Cl2)
is a more effective de-icer at lower temperatures than sodium
chloride (NaCl). It attracts moisture and tends to stay on
the road surface longer than NaCl (Trotta, 1988). A brine is
commonly used for pre-wetting. Ca Cl2 has the same
problems with chloride activity, and is more costly, than NaCl.

Calcium Magnesium Acetate has a
low environmental impact but can contribute to biochemical
oxygen demand (BOD) in small bodies of surface water. It is
an effective agent for anti-icing (Keep et al, 1995) although
a little less effective as a de-icer than NaCl. The main reason
it is not more widely used is its high purchase cost relative
to NaCl.

Magnesium Chloride (MgCl2),
like Ca Cl2 is also a more effective de-icer at
lower temperatures than sodium chloride NaCl. It also attracts
moisture and tends to stay on the road surface longer than
NaCl. Brines are commonly used for pre-wetting. MgCl2 has
the same problems with chloride activity, and is somewhat more
costly, than NaCl.

Potassium Acetate is used
as a base for several commercial chloride-free liquid de-icer
formulations. The reputed advantages include low corrosion,
relatively high performance and low environmental impact. The
cost is high.

Potassium Chloride (KCl) is similar
to calcium and magnesium chlorides. It is also a more effective
de-icer at lower temperatures than NaCl, is hygroscopic (attracts
moisture), and tends to stay on the road surface longer than
NaCl. Brines are commonly used for pre-wetting. KCl has the
same problems with chloride activity, and is somewhat more
costly, than the more common NaCl.

Sodium Salts of Carboxylic Acids are mixtures of the sodium salts
of fatty acids with low molecular weight, such as sodium
formate, and have demonstrated de-icing properties comparable
to sodium chloride. Such chemicals can be used to reduce
the amount of chloride released in winter maintenance operations,
but sodium would still be an issue. Such chemicals are still
largely under development. Their use should be carefully
controlled.

Urea is not as effective as NaCl but is less corrosive. It has
less effect on soil and vegetation than NaCl but promotes
algal growth and biochemical oxygen demand BOD in surface
waters. Urea is used at airports to avoid corrosion of aircraft.

There are
various liquid and solid formulations of these chemicals. Each
winter maintenance operation must determine the best choice
for its own program. There are alternatives to roadsalt available
that cause less environmental damage and more are being developed.
Regular reviews of products available in the market and discussion
with other communities regarding alternative de-icers are recommended.
The Ministry of Transportation and Highways constantly carries
out reviews and analyses of de-icers. Capital cost is usually
the major problem with use of such materials.

There are
alternative ways to reduce impact of roadsalt to the environment.
While simply modifying existing winter maintenance practices
slightly is one technique, there are some other measures that
can be applied. A few such measures are listed below:

Education
of road maintenance staff to reduce the quantities of salt
used and to prevent the unnecessary use of salt.

Limiting
salt application to specific areas that need it the most
such as steep inclines, bus routes and main thoroughfares.

Establishment
of buffer zones and filter strips on the sides of roadways
to prevent direct spray and runoff from reaching sensitive
surface waters and vegetation.

Construction
of drainage systems that direct salt laden runoff away from
sensitive areas. When local ground water quality is a concern,
catchbasins, drainpipes, lined ditches, and impervious berms
beneath the roadside are all effective for directing salt
away from the problem areas. This is more cost-effective
in urban areas.

Identification
of salt-sensitive areas, ecosystems, waterbodies and aquifers
which require special reductions in the application of salt
on relevant stretches of roadway. Alternative chemicals,
more efficient use of salt, reliance on abrasives and changes
to the road surface are possible means of achieving such
a reduction.

One measure
which would allow for vast reductions in winter maintenance
would be to increase public awareness of the potentially harmful
effects of de-icing chemicals on the environment and to secure
the public's cooperation in reducing the need for application
of salt on roads by lowering speed limits under icy conditions.
In some places where the environment is very sensitive to human
activity and important to the public, lower speed limits and
other driving restrictions have been imposed.

In Japan,
commuters drive more slowly in the winter months and use special
soft rubber winter tires that grip the road surface almost
as well as studded tires (Minsk et al, no date). In parts of
the Netherlands where drinking water quality is an issue, speed
limits are sometimes controlled by road conditions and the
public does not expect to drive the same speed all year round
(Leppänen, 1996). Anti-lock brakes on vehicles will also
help, to some extent, to reduce accidents on ice and snow.

In many
cases, particularly in cities, snow cannot be pushed off the
road-side, but must be picked up and dumped somewhere. What
to do with large quantities of snow has always been a problem.
In many places it has been dumped into water, rivers and lakes,
which gets rid of it effectively but causes contamination (Scott,
1980).

However,
when it is scraped off the streets, snow includes salt, sand,
organics, metals and debris and these contaminants are of concern
Table 2. The quality of the snow may also be affected by the
town and the contaminants found on the streets; snow from Trail
had high metal levels and failed Daphnia and Selanastrum toxicity
tests (Antcliffe and Colwell, 1998). If snow is left on the
streets to melt and runs into storm sewers much of this material
ends up in the rivers, although some solids do settle out in
retention basins where these exist. If the snow is piled on
empty lots the solids are removed but much of the soluble salts
will eventually find their way into ground water or surface
waters. There is no fully satisfactory solution, but there
are some compromises which lessen the impacts to water and
sediment quality. These include:

do not dump snow from roads into lakes, ponds, swamps or
other standing water bodies;

do not
dump snow from roads in small community streams — dump
it only in large rivers with a high dilution flow;

snow
dumped in high flow rivers should only be fresh new snow
which has not been sanded or salted and has low concentrations
of sediment or other contaminants;

contaminated
snow (snow which has been on the road for some time and has
been salted or sanded) should be dumped on non-porous land
and allowed to melt. The land should be situated such that
there will be no overland flow of the melt water into water
courses;

the same
location should not be used continuously over many years
where the soil conditions could lead to ground water contamination.

snow
includes salt, sand, organics,
metals and debris when it is
scraped off the streets

There is
an alternative method which has been tested in the Quebec City
of Cap-Rouge (CWWA Bulletin, 1999) which may be of value in many
locations. It save trucking costs, reduces the need for large
areas of land to store snow while it melts and eliminates the
dumping of contaminants in the rivers or allowing them to percolate
into ground water. Between May and October St. Lawrence River
water is chlorinated, heated using solar panels and injected
into an aquifer where it maintains a temperature of 15° to
28° over winter. During the winter this warm water is pumped
into a large underground concrete reservoir into which the collected
snow is dumped. The snow melts and the water flows out of the
reservoir back to the river; the solids settle to the bottom
of the reservoir for later collection and disposal.

Roadsalt
may contain a number of contaminants, some deliberately added
and others incidental. The source of roadsalt used should be
analysed to make sure it has no harmful materials in it. Anti-caking
compounds are sometimes added and some of these contain cyanide
which is very toxic and should be avoided. Do not assume
roadsalt is just NaCl. The commercial grade used for roadsalt is impure
and will contain contaminants, some of which may be toxic.
However, apart from the cyanide the concentrations are generally
too low to be of concern.

When large
purchases of roadsalt are going to be made, insist on an analysis
of the product first. Testing by MOTH over the years indicates
that the normal mixture supplied is about 99% NaCl and only
1% contaminants, mostly soil particles.

Table 2
gives some contaminants in snow removed from roads in Toronto.
Not all of these contaminants resulted from roadsalt application.
With the obvious exception of the chlorides, most came from
the roads and the cars themselves. After normal dilutions of
at least 10:1 or 20:1 they would not constitute a water quality
problem.

Table 2. Contaminants in Snow Removed from Toronto Roads

Parameters
(total)

Concentration in
mg per litre
of water

Concentration in
pounds per ton
of snow

solids

10500

21

chlorides

2250

4.4

lead

41.5

0.08

iron

41.5

0.08

phosphorus

2.4

0.005

BOD

57

0.114

based on 5
samples of Toronto street snow.

The concentrations of all these contaminants exceed the BC
Water Quality Criteria for Aquatic Life; undiluted melted
snow
would not meet water quality guidelines to support aquatic life.

Roadsalt was
often stored in piles near the stretch of road where experience
indicated it would be needed. Often there were neither floor
nor roof provided for the piles. Historically, ground water
contamination by roadsalt was caused by runoff and infiltration
of NaCl from these salt storage piles. A properly constructed
storage facility, and transfer procedures which avoid spillage,
should virtually eliminate the risk to water quality from
roadsalt storage facilities.

For
further information, see the document on salt storage by
the BC Ministry of Transportation and Highways (Buchanan,
1996) and a more general reference document on road maintenance
(BC MOTH, 1995); both can be found in the Information Resources
section that follows. The following are suggestions for
building and maintaining salt storage facilities to help
minimize the risk of water quality impairment:

Locate
the stile well away from populated areas, wells, ground water
sources and surface waters.

Construct
a permanent roof, impervious to precipitation.

Drain
storage site runoff via tiled ditches or pipes to a collection
area, preferably a specially designed sump area.

Install
a plastic liner beneath the storage and loading areas to
ensure that spilled salt does not migrate through the soil
and into near-by ground water.

Keep
the loading areas clear of spilled or scattered salt.

Make
the floor out of high quality concrete: air-entrained and
sealed to prevent spalling, or cover the concrete floor in
asphalt.

Ensure
that the floor or pad has a slope between 2 and 5 percent
to allow any moisture to drain into the collection sump.

For very
small and temporary sites that do not warrant a structure,
keep the salt, or salt/sand mixture covered with a waterproof
material to prevent runoff and store it on waterproof ground
sheets to prevent runoff and absorption of moisture from
the ground.

There
are many publications on the application of salt to roads
and general winter maintenance. An Internet search using
key words such as deicing, de-icing, anti-icing, road salt,
roadsalt, salt, snow and ice will likely get results for
those looking for more or new information on the topic. It
is also useful to inquire at MOTH yards directly as they
often have the resources and information to answer questions.

The
internet may give additional contacts, examples of research,
operational programs, and other useful information. Some
website addresses that contain information and links to other
sites on roadsalt are listed below. Other uncited publications
of special interest are listed as well. Remember that internet
sites are ephemeral, not permanent, and the list given here
will rapidly become dated.

Antcliffe, B. L. and S. Colwell. 1998. Analysis
of Snowmelt Samples Collected from the Cities of Trail and
Revelstoke, British Columbia, During the Winter of 1997/1998.
Department of Fisheries and Oceans Canada, Habitat Enhancement
Branch, Vancouver, BC.

Menzies, T. R. 1992. An overview of the National Research
Council Study of the Comparative Costs of using Rock Salt and
CMA for Highway De-Icing. In: F. M. D'Itri Editor. Chemical
De-icers and the Environment. Lewis Publishers, INC. p283-301.Mergenmeier, A. 1995. What You need to Know about Prewetting
De-Icers. Better Roads. June: 29-31.